1. Field of the Invention
This invention is related to chemical composition delivery systems and methods, especially to the chemical delivery systems for electronics specialty chemical compositions, including CMP slurries for wafer polishing.
2. Related Art
Process chemicals for semiconductor manufacturing are usually delivered from bulk containers to user stations with so called chemical delivery systems. High-pressure inert gases, such as nitrogen gas, have become popular for driving chemical compositions from chemical containers to user stations. Compared to the delivery systems having a pump, systems employing high-pressure inert gas for chemical delivery have the advantages of delivery from further distance, and also smooth and pulse-less delivery, thus avoiding impurity shedding from the components of the delivery system.
Although the advantages of such a chemical delivery method have been realized and the method has been practiced in large extent, some concerns and problems have arisen when some of the semiconductor process chemical compositions are delivered with this type of delivery system. For example, inert gas, such as nitrogen gas, will readily dissolve into some of these process chemicals during compression process and eventually form dry spots on wafers. These dry spots become manufacturing defects and seriously reduce the production yield of semiconductor manufacturing. To avoid and eliminate the problem of gas dissolving in chemical compositions, a new delivery system with a bladder installed inside the pressure vessel has been invented. With this method and apparatus, high-pressure nitrogen gas is filled into the bladder to pressurize chemical compositions outside of the bladder. Since there is no direct contact between the chemical composition and nitrogen gas, dissolving of nitrogen gas into chemicals is avoided. Furthermore, chemical compositions will not change in assay due to chemical evaporation.
When delivering aqueous chemical compositions using direct contact with an inert gas, such as slurry compositions used for polishing wafer surfaces, water and other chemical compounds in the chemical composition at the composition surface and composition residuals on the container surfaces will be rapidly lost into the inert gas when the high-pressure inert gas directly contacts with the chemical composition. This is because inert gases are usually very dry and very pure. Amounts of chemical compounds such as water in the chemical composition will change because of evaporation. This change in chemical composition may make the chemical composition function improperly when it is used in the semiconductor manufacturing process. When water evaporates into inert gas, a dry film or dry residuals could be formed with much less water and more concentrated compositions of less volatility. In the case of slurry compositions, this dry film or dry residuals will be in the form of agglomerated particles of larger sizes. These agglomerated particles eventually will be delivered with chemical compositions to user stations and produce scratches on wafer surfaces. This problem could be solved by using the above mentioned bladder technology by preventing the direct contact of nitrogen gas with chemical composition. With this technology, a thin and flexible material that is compatible with the chemical composition must be carefully selected for the bladder.
To overcome the shortcomings of water evaporation into inert gas, a moisturizer can be used to moisturize the nitrogen gas prior to its going into the pressure vessels to pressurize chemical compositions, such as depicted in U.S. Pat. No. 6,076,541. When the moisturized nitrogen gas contacts with chemical compositions, mass transfer of water in the nitrogen gas and the chemical composition is significantly reduced or completely eliminated. Therefore, there is no, or very little, dry residuals or dry film formed within the pressure vessels. However, there are still some drawbacks. First, more space will be needed for accommodating a humidifier near to the pressure vessel. This could be a serious problem because in a semiconductor manufacturing facility, space is always limited. Additional equipment to occupy space is not always permitted and space is not always affordable. Second, moisturized nitrogen gas may create some problems in the system operation. Since moisturized nitrogen flows through a relative long line into the pressure vessel, moisture in nitrogen gas can be condensed in the line because of changes of physical condition. This condensate could block up valves and make the valves malfunction. The condensate could also be carried further into the pressure vessel to dilute the chemical compositions. Chemical composition change by such kind of dilution is forbidden because the composition of chemical compositions must be precisely controlled to meet user""s specification. Further, some chemical compositions, such as hydrogen peroxide in the chemical composition, will evaporate into high purity inert gas even though it is moisturized. Hence, chemical compositions will change when the chemical composition is delivered with such a method although such a change in chemical composition may not be a serious problem for some cases.
It would therefore be advantageous, and an advance in the chemical delivery art, if chemical delivery systems and methods could be designed that reduce or avoid the above-noted drawbacks.
In accordance with the present invention, novel and simple apparatus and methods are proposed to reduce or eliminate the problems of dry residuals and dry film during liquid chemical composition delivery with pressure vessels, as well as problems associated with previously known humidification systems. As used herein the terms xe2x80x9csystemxe2x80x9d and xe2x80x9capparatusxe2x80x9d are used interchangeably.
As used herein the term xe2x80x9cliquid chemical compositionxe2x80x9d means:
a fluid that flows under the presence of pressure, gravity, or combination;
may be Newtonian or non-Newtonian fluid;
may be aqueous, non-aqueous or combination;
may be a combination of components (liquid, solid, and gaseous).
Preferably, liquid chemical compositions which may benefit from the present invention are substantially aqueous, Newtonian fluids having a combination of ingredients, including, in some embodiments, one or more organic compounds, such as reactive diluents, non-reactive diluents, solvents, co-solvents, coupling agents, and the like, and abrasive matter, for example dispersed in individual particles, or agglomerates of individual particles. Chemical-mechanical planarization slurries and chemical-mechanical polishing slurries are two preferred liquid chemical compositions. Suitable organic solvents might include organic alcohols, ketones, acids and the like, isopropyl alcohol, for example.
A first aspect of the invention is an apparatus for delivery of liquid chemical compositions. A first apparatus embodiment comprises:
a) a pressure vessel comprising an inlet and an outlet for a liquid chemical composition, and a vapor space, the pressure vessel adapted to contain the liquid chemical composition, the liquid chemical composition having a vaporizable portion (preferably a major portion of water) therein;
b) means for contacting (preferably bubbling) a dry, preferably high purity inert gas with at least a portion of the liquid chemical composition in the pressure vessel to transfer at least a portion of the vaporizable portion from the chemical composition to the inert gas to form a wet inert gas in the vapor space; and
c) means for pressurizing the chemical composition out of the vessel using the wet, high purity inert gas.
Preferred apparatus within this embodiment are those wherein the inlet and the outlet are each legs of a tee connection, a remaining leg of the tee connected to the pressure vessel. Also preferred are apparatus wherein the dry, preferably high purity inert gas is adapted to be sparged into the pressure vessel near a bottom of the vessel through an inert gas inlet conduit, the inert gas inlet conduit having an exit end, preferably the exit end of the inert gas inlet having a sparging device attached thereto.
As used herein the term xe2x80x9cdryxe2x80x9d means the inert gas preferably has a moisture content less than 10 percent relative humidity (RH), more preferably less than 1 percent RH. xe2x80x9cHigh purityxe2x80x9d as used herein when referenced to the inert gas means the inert gas has less than 10 parts per million (ppm) total impurity (inorganic compounds and organic compounds), more preferably less than 5 ppm. xe2x80x9cUltra high purityxe2x80x9d as used herein when referenced to the inert gas means the inert gas has less than 1 part per billion total impurity (inorganic compounds and organic compounds). One preferred dry inert gas is that referenced in Semiconductor Equipment and Materials International (SEMI) standard C3.29-96, Standard for Nitrogen, Bulk Gaseous, 99.9995% Quality (1999), incorporated herein by reference. The term xe2x80x9cwetxe2x80x9d means a gas composition having components selected from the group consisting of water vapor, organic vapor, inorganic vapor, and combinations thereof.
A second apparatus embodiment of the invention for delivery of liquid chemical compositions comprises:
a) a pressure vessel comprising a first compartment and a second compartment, the first compartment and the second compartment divided by a dividing element;
b) the first compartment connected to an inlet conduit for a wetting composition, and a waste conduit for allowing the wetting composition to be delivered to waste, the dividing element functioning to establish a liquid level of the wetting composition in the first compartment, the first compartment also having a dry, preferably high purity inert gas inlet conduit having an end positioned (preferably adapted to be submerged into the liquid chemical composition to be delivered to waste) to provide contact in the first compartment between the inert gas and the wetting composition to form a wet inert gas, the first compartment further having an outlet for the wet inert gas;
c) the outlet for the wet inert gas connected to the second compartment by a wet inert gas conduit;
d) the second compartment connected to an inlet conduit and an outlet conduit for a liquid chemical composition, and a vapor space, the vapor space connected to the first compartment via the wet inert gas conduit.
Preferred apparatus of the second embodiment are those wherein the conduit is part of a means for monitoring level of the liquid chemical composition inside the second compartment. Also preferred are those apparatus wherein the wet inert gas conduit includes a means for removing liquid droplets from the wet inert gas, such means selected from screens, meshes, mist eliminators, coalescers, adsorbent materials, absorbent materials, molecular sieves, zeolites, filters, heat exchangers, condensers, cryocoolers and the like.
A third apparatus embodiment for delivery of liquid chemical compositions comprises:
a) a pressure vessel comprising a first compartment and a second compartment, the first compartment and the second compartment divided by a dividing element;
b) the first compartment connected to an inlet conduit for spraying a wetting composition into the first compartment, and a waste conduit for allowing the wetting composition to be delivered to waste, the inlet conduit terminating in a means for spraying the wetting composition into the first compartment, the dividing element functioning to establish a level of the wetting composition in the first compartment, the first compartment also connected to a gas inlet conduit for a dry, preferably high purity inert gas, the gas inlet conduit having a terminal end positioned (preferably above a level of the sprayed portion of liquid chemical composition to be delivered to waste) to allow contact in the first compartment between the inert gas and the wetting composition to form a wet inert gas, the first compartment further having an outlet for the wet inert gas;
c) the outlet for the wet inert gas connected to the second compartment by a wet inert gas conduit;
d) the second compartment having an inlet conduit and an outlet conduit for a liquid chemical composition, and a vapor space, the vapor space connected to the first compartment via the wet inert gas conduit.
A fourth apparatus embodiment of the invention for delivery of liquid chemical compositions comprises:
a) a pressure vessel comprising a first compartment and a second compartment, the first compartment and the second compartment divided by a dividing element;
b) the first compartment connected an inlet conduit for spraying a wetting composition into a chamber formed by a housing, and a waste conduit for allowing the wetting composition to be delivered to waste, the inlet conduit terminating in a means for spraying the wetting composition into the chamber, (the dividing element preferably functioning to establish a level of the wetting composition in the chamber), the housing also connected to a gas inlet conduit for a dry, preferably high purity inert gas, the gas inlet conduit and housing adapted to allow contact between the inert gas and the wetting composition in the chamber, the housing further having means for allowing wet inert gas to move into the first compartment;
c) the dividing element having means for allowing passage of said wet inert gas from the first compartment to the second compartment;
d) the second compartment connected to an inlet conduit and an outlet conduit for a liquid chemical composition, and a vapor space, the vapor space fluidly connected to the first compartment via the means for allowing passage in the dividing element.
A fifth apparatus embodiment is a slight modification of the fourth embodiment, and includes the feature that the housing has one or more means for allowing the wetting composition, after contacting the dry inert gas, to traverse through the housing and fall into the second compartment. Preferably, the means for allowing the wetting composition to traverse through the housing are located at location selected from the group consisting of the bottom of the housing, the sidewall of the housing, or both.
It will be understood as included within the scope of the invention that there may exist a plurality of housings inside the first compartment, each having a gas inlet conduit and a conduit for spraying wetting composition into each housing.
A second aspect of the invention includes methods of delivering a liquid chemical composition. A first preferred method embodiment comprises:
a) filling a pressure vessel with a liquid chemical composition comprising a vaporizable component (preferably including moisture), the pressure vessel having a vapor space and adapted to contain the liquid chemical composition;
b) contacting (preferably by bubbling) a dry, preferably high purity inert gas with at least a portion of the liquid chemical composition in the pressure vessel to transfer at least a portion of the vaporizable composition from the liquid chemical composition to the dry inert gas to form a wet inert gas in the vapor space; and
c) pressurizing the liquid chemical composition out of the pressure vessel using the wet inert gas in the vapor space.
A second method embodiment of delivering a liquid chemical composition comprises the steps of:
a) providing a pressure vessel comprising a first compartment and a second compartment, the first compartment and the second compartment divided by a dividing element;
b) at least partially filling the first compartment with a wetting composition, the dividing element functioning to establish a level of the wetting composition in the first compartment;
c) flowing a dry, preferably high purity inert gas into the first compartment in a manner to provide contact between the inert gas and the wetting composition, thus forming a wet inert gas, the first compartment further connected to an outlet conduit for the wet inert gas;
d) flowing the wet inert gas into the second compartment through a conduit; and
e) substantially filling the second compartment with a liquid chemical composition allowing a vapor space, the second compartment connected to the first compartment via the conduit.
A third method embodiment of delivering a liquid chemical composition comprises the steps of:
a) providing a pressure vessel comprising a first compartment and a second compartment, the first compartment and the second compartment divided by a dividing element;
b) spraying into the first compartment a wetting composition, the dividing element functioning to establish a level of the wetting composition in the first compartment;
c) flowing a dry, preferably high purity inert gas into the first compartment (preferably above a level of the wetting composition), and contacting the inert gas with the wetting composition, thus forming a wet inert gas;
d) flowing the wet inert gas from the first compartment into the second compartment through a conduit; and
e) substantially filling the second compartment with a liquid chemical composition, allowing a vapor space, the second compartment connected to the first compartment via the conduit.
A fourth method embodiment of delivering a chemical composition comprises the steps of:
a) providing a pressure vessel comprising a first compartment and a second compartment, the first compartment and the second compartment divided by a dividing element, the first compartment having a chamber formed by a housing;
b) spraying into the chamber a wetting composition, the dividing element functioning to establish a level of the wetting composition in the chamber;
c) flowing a dry, preferably high purity inert gas into the chamber to provide contact between the inert gas and the wetting composition, thus forming a wet inert gas;
d) flowing the wet inert gas into the second compartment through a conduit; and
e) substantially filling the second compartment with a liquid chemical composition, allowing a vapor space, the vapor space connected to the first compartment via the conduit.
The first apparatus embodiment of the invention allows contacting a dry, preferably high purity inert gas with a wetting composition, the wetting composition being the liquid chemical composition to be delivered. Contacting occurs in a pressure vessel to form a wet inert gas, which is then used to pressurize the liquid chemical composition out of the pressure vessel. Therefore, no additional space is needed for an external humidifier as in previous apparatus and methods. Since preferably a very small amount of vapor is needed to saturate the dry inert gas, the assay of the liquid chemical composition will not be substantially affected when the wetting composition is the liquid chemical composition being delivered. The vapor content of the wet inert gas can also be easily controlled by carefully flowing the dry inert gas through the liquid chemical composition, in the first embodiment.
Other preferred embodiments of the presented invention feature two compartments within a pressure vessel of integral body. Liquid chemical composition to be delivered is supplied into one compartment, and a relatively small amount of a wetting composition (which may be the liquid chemical composition being delivered, if desired) and inert gas is supplied into another compartment in such a manner as to cause contact between the dry inert gas and the wetting composition. The two compartments communicate with each other through means described herein. Hence, the liquid chemical composition is propelled with wet inert gas that comprises chemical vapors, preferably water vapor, but not limited thereto. The problem of liquid chemical being lost into the dry inert gas is prevented while the dry residual problem is eliminated at the same time.
With one preferred embodiment, the two compartments as mentioned above communicate with each other through a conduit, allowing wet inert gas to flow into and out of the compartments.
With an additional preferred embodiment, the two compartments as mentioned above communicate with each other through a series of means, preferably small openings such as holes, louvers, channels, and the like in the dividing means separating the two compartments.
All of the embodiments in this invention are provided with necessary control and isolation valves for discharging and recharging liquid chemical compositions into the pressure vessels, introducing in and draining out of liquid chemical composition, and filling and releasing inert gas. The preferred embodiments of the pressure vessels can be operated for delivering chemical compositions with one, or more than one, pressure vessels in parallel. Two or more pressure vessels are usually installed in parallel to continuously deliver liquid chemical compositions. Preferred embodiments of pressure vessels of this invention can also be arranged in series to recharge liquid chemical compositions from one pressure vessel to another.
These and other advantages and aspects of the invention are demonstrated with reference to the following drawings and description of preferred embodiments, although not limited thereto.